Computer started hanging, then would boot with a question mark. When I booted it on a utility drive, the internal drive showed briefly, then disappeared for good. Purchased a replacement drive. When I booted off a Mavericks install drive, the new drive doesn't show. Same when booting the MBP off a utility drive. New drive doesn't show. Pulled the new drive and formatted it GUID, reinstalled, doesn't show. Meanwhile, the old drive is showing on my imac in an external case. Suggestions on what might be wrong on the MBP? Cable? Bus? Board? Anyone with experience with this type of problem?